STM investigation of local transport properties on manganites

S. Seiro, Y. Fasano, I. Maggio-Aprile, O. Kuffer, Ø. Fischer

DPMC, University of Geneva, Quai Ernest Ansermet 24, 1511 Geneva, Switzerland

The ever-increasing number of experimental and theoretical works in support of the percolation of intrinsic inhomogeneities at the origin of the colossal magnetoresistance (CMR) effect in manganites is calling for a comprehensive study of transport properties at the nanoscale. This can be performed by scanning tunnelling microscopy (STM), which furnishes topographic and spectroscopic maps down to the atomic scale. Spectroscopy is nevertheless an extremely surface sensitive tool and measured characteristics may not be representative of bulk behaviour. In order to probe bulk-like properties, we have implemented a related technique called potentiometry, in which the potential drop induced by a current flowing thorough the sample is recorded as a function of the position. We present potentiometry measurements performed as a function of temperature in a La0.7Ca0.3MnO3 thin film.